Question

A point source emits sound equally in all directions in a non-absorbing medium. Two points $P$ and $Q$ are at distance of $2m$ and $3m$ respectively from the source. The ratio of the intensities of the wave at $P$ and $Q$ is:

• A. $9:4$
• B. $2:3$
• C. $3:2$
• D. $4:9$

Answer 1

Answer: (A)

$9:4$

intensity is inversely proportional to $r^2$

$I_1:I_2=r_2^2:r_1^2=3^2:2^2=9:4$